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Jung, Youngeun,Kim, Ikyon American Chemical Society 2015 Journal of organic chemistry Vol.80 No.3
<P>Described herein is a highly efficient total synthesis of brazilin from commercially available starting materials in 9 steps with 70% overall yield. Mitsunobu coupling followed by In(III)-catalyzed alkyne-aldehyde metathesis allowed for rapid construction of brazilin core skeleton in quantitative yield. Subsequent modulation of oxidation levels and acid-catalyzed cyclization led to the trimethyl ether of brazilin. Asymmetric dihydroxylation of the key intermediate was also demonstrated, which would permit asymmetric access to (+)-brazilin.</P>
A concise synthetic approach to brazilin <i>via</i> Pd-catalyzed allylic arylation
Jung, Youngeun,Kim, Ikyon The Royal Society of Chemistry 2015 Organic & Biomolecular Chemistry Vol.13 No.14
<P>A short synthetic route to the trimethyl ether of brazilin was developed in 6 steps from 7-methoxychromene with 78% overall yield. Regioselective installation of a formyl group onto 7-methoxychromene followed by reduction and acetylation afforded allylic acetate. Palladium-catalyzed allylic coupling of allylic acetate with arylboronic acid provided direct access to 3-benzylchromene which was converted to the target molecule upon ensuing dihydroxylation and acid-catalyzed cyclization in a highly concise manner.</P> <P>Graphic Abstract</P><P>A short synthetic route to the trimethyl ether of brazilin was developed in 6 steps from 7-methoxychromene with 78% overall yield. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5ob00216h'> </P>
Deformylative Intramolecular Hydroarylation: Synthesis of Benzo[<i>e</i>]pyrido[1,2-<i>a</i>]indoles
Jung, Youngeun,Kim, Ikyon American Chemical Society 2015 ORGANIC LETTERS Vol.17 No.18
<P>Attempted cyclization of indolizines bearing both formyl and alkyne groups under acid catalysis provided benzo[<I>e</I>]pyrido[1,2-<I>a</I>]indoles with an aryl substituent at the C6 position as major products, along with the expected C5-acylated benzo[<I>e</I>]pyrido[1,2-<I>a</I>]indoles as minor ones, which resulted from preferential deformylative intramolecular hydroarylation instead of intended alkyne-carbonyl metathesis.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2015/orlef7.2015.17.issue-18/acs.orglett.5b02331/production/images/medium/ol-2015-02331m_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol5b02331'>ACS Electronic Supporting Info</A></P>
Photo-triggered fluorescent labelling of recombinant proteins in live cells
Jung, Deokho,Sato, Kohei,Min, Kyoungmi,Shigenaga, Akira,Jung, Juyeon,Otaka, Akira,Kwon, Youngeun The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.47
<P>A method to photo-chemically trigger fluorescent labelling of proteins in live cells is developed. The approach is based on photo-caged split-intein mediated conditional protein trans-splicing reaction and enabled background-free fluorescent labelling of target proteins with the necessary spatiotemporal control.</P> <P>Graphic Abstract</P><P>A method to photo-chemically trigger fluorescent labelling of proteins in live cells is developed for background-free fluorescent labelling of target proteins with the necessary spatiotemporal control. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cc01067e'> </P>
Chemical biology-based approaches on fluorescent labeling of proteins in live cells
Jung, Deokho,Min, Kyoungmi,Jung, Juyeon,Jang, Wonhee,Kwon, Youngeun The Royal Society of Chemistry 2013 Molecular bioSystems Vol.9 No.5
<P>Recently, significant advances have been made in live cell imaging owing to the rapid development of selective labeling of proteins <I>in vivo</I>. Green fluorescent protein (GFP) was the first example of fluorescent reporters genetically introduced to protein of interest (POI). While GFP and various types of engineered fluorescent proteins (FPs) have been actively used for live cell imaging for many years, the size and the limited windows of fluorescent spectra of GFP and its variants set limits on possible applications. In order to complement FP-based labeling methods, alternative approaches that allow incorporation of synthetic fluorescent probes to target POIs were developed. Synthetic fluorescent probes are smaller than fluorescent proteins, often have improved photochemical properties, and offer a larger variety of colors. These synthetic probes can be introduced to POIs selectively by numerous approaches that can be largely categorized into chemical recognition-based labeling, which utilizes metal-chelating peptide tags and fluorophore-carrying metal complexes, and biological recognition-based labeling, such as (1) specific non-covalent binding between an enzyme tag and its fluorophore-carrying substrate, (2) self-modification of protein tags using substrate variants conjugated to fluorophores, (3) enzymatic reaction to generate a covalent binding between a small molecule substrate and a peptide tag, and (4) split-intein-based C-terminal labeling of target proteins. The chemical recognition-based labeling reaction often suffers from compromised selectivity of metal–ligand interaction in the cytosolic environment, consequently producing high background signals. Use of protein–substrate interactions or enzyme-mediated reactions generally shows improved specificity but each method has its limitations. Some examples are the presence of large linker protein, restriction on the choice of introducible probes due to the substrate specificity of enzymes, and competitive reaction mediated by an endogenous analogue of the introduced protein tag. These limitations have been addressed, in part, by the split-intein-based labeling approach, which introduces fluorescent probes with a minimal size (∼4 amino acids) peptide tag. In this review, the advantages and the limitations of each labeling method are discussed.</P> <P>Graphic Abstract</P><P>This review summarizes various approaches to incorporate synthetic fluorescent probes to target proteins in live cells as well as current efforts to control the fluorescent signal using external stimuli. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2mb25422k'> </P>
Musclelike joint mechanism driven by dielectric elastomer actuator for robotic applications
Jung, Ho Sang,Cho, Kyeong Ho,Park, Jae Hyeong,Yang, Sang Yul,Kim, Youngeun,Kim, Kihyeon,Nguyen, Canh Toan,Phung, Hoa,Hoang, Phi Tien,Moon, Hyungpil,Koo, Ja Choon,Choi, Hyouk Ryeol Institute of Physics Publishing 2018 Smart materials & structures Vol.27 No.7
<P>The purpose of this study is to develop an artificial muscle actuator suitable for robotic applications, and to demonstrate the feasibility of applying this actuator to an arm mechanism, and controlling it delicately and smoothly like a human being. To accomplish this, we perform the procedures that integrate the soft actuator, called the single body dielectric elastomer actuator, which is very flexible and capable of high speed operation, and the displacement amplification mechanism called the sliding filament joint mechanism, which mimics the sliding filament model of human muscles. In this paper, we describe the characteristics and control method of the actuation system that consists of actuator, mechanism, and embedded controller, and show the experimental results of the closed-loop position and static stiffness control of the robotic arm application. Finally, based on the results, we evaluate the performance of this application.</P>
Jung, Kyung-Hwa,Lee, Kye Seok,Kim, Youngeun,Park, Soojin,Hong, Moochang,Shin, Minkyu,Bae, Hyunsu The Society of Korean Medicine 2013 대한한의학회지 Vol.34 No.2
Objectives: In the present study, we evaluate the anti-inflammatory effect of Lonicerae Flos on cigarette-induced lung inflammatory responses in animal model of chronic obstructive pulmonary diseases (COPD). Methods: To inspect the effects of Lonicerae Flos, we evaluated Lonicerae Flos functions in vivo including immune cell profiles in bronchoalveolar lavage (BAL) fluid, cytokine production and tissue morphological changes. Results: Lonicerae Flos significantly inhibited immune cell infiltrations into the BAL fluid (neutrophils, macrophages, lymphocytes). TNF-${\alpha}$, and interleukin-6 (IL-6) were substantially decreased in the BAL fluid of Lonicerae Flos-treated mice compared with cigarette-exposed control mice. In addition, the hypertrophy of goblet cells in the epithelial cells was reduced in both Lonicerae Flos- and roflumilast-treated mice. Conclusions: The results of this study provide evidence that treatment with Lonicerae Flos exerts strong therapeutic effects against cigarette-induced lung inflammation in vivo. Therefore, this herbal medicine may represent a novel therapeutic agent for lung inflammation in general, as well as a specific agent for the treatment of COPD.